It is known from U.S. Pat. No. 3,731,495 to integrate an air separation unit (ASU) with a gas turbine by removing compressed air from the gas turbine compressor, sending it to the ASU and sending a nitrogen enriched gas from the ASU upstream of the expander of the gas turbine. In this case, the expander of the gas turbine is coupled to the gas turbine compressor.
It is known from U.S. Pat. No. 4,566,885 and U.S. Pat. No. 5,139,548 to couple the compressors of two gas turbines with the cycle compressors of a refrigeration cycle, using a multicomponent refrigerant (MCR), of a natural gas liquefaction process.
At certain sites, it may be desired to transform a first stream of natural gas into liquefied natural gas and a second stream of natural gas at least one product of the conversion of the natural gas, such as methanol, DME or the product of a Fischer Tropsch reaction. The conversion reaction frequently requires the supply of large amounts of gaseous oxygen. Heat generated by the reaction is commonly used to raise steam which is then expanded in a steam turbine to generate electricity.
An object of the invention is to reduce the costs of a production complex which simultaneously produces from the same natural gas source both liquefied natural gas and a product of the conversion of the natural gas, such as methanol, dimethyl ethers or a Fischer Tropsch product, by integrating an air separation unit, a gas turbine, a natural gas conversion unit and a natural gas liquefaction unit.
Typically in the prior art, the power requirements are provided by a steam turbine powering the MAC compressor of the ASU as shown in U.S. Pat. Nos. 3,868,817, 4,099,383 and 4,184,322 and two gas turbines powering the multicomponent refrigerant cycle and propane cycle of the natural gas liquefier as mentioned above.
The integrated process of the invention uses only a single gas turbine.